To enable leads to be visible in your VerticalResponse account you must:
1. In Salesforce Classic, click Setup.
2. Click Customize (under Build).
3. Click Leads.
4. Click Fields to view the Leads Fields workspace.
5. Click Email Opt Out in the "Field Label" column.
6. Click Set Field-Level Security.
7. Click the checkbox beside each Field-Level Security to make sure it is visible.